Which actor accidentally cut his hand and continued filming in character on the set of "Django Unchained"?

I just watched a special on HBO about Sergio Leone, who was responsible for the term "Spaghetti Western" being coined. What a brilliant man who was very particular about every aspect of his films, including the music. Django was a very powerful and moving film, Tarantino learned a lot from watching the Leone films.

Too easy; at least include another actor who was in the movie!